130/80 vs 130/100.....the first number is the width of the tire and the second is the height relative to the width is what I think these numbers represent....if this is true....the "100" would be a taller sidewall.....

n'est pas?

And , yes, the EXC swingarms can take in water and it is a good idea to drill a 1/8 hole in the bottom of each swing arm a few inches from the back end....and check the holes occasionally as they can get plugged.

R U sure? I have a 100/100 rear and the sidewall is really short.
The 100/80 has a taller sidewall.